According to the examinations by the inventors of the present invention, techniques as follows are known in the field of microcomputers in notebook PCs.
For example, in a notebook PC according to the prior art, a microcomputer in a keyboard/power management controller is provided with a keyboard BIOS that controls key scan and input devices such as a keyboard and a mouse and a power management BIOS that controls a battery and a fan, and the microcomputer is controlled by programs of these two BIOSes. In a notebook PC having such a microcomputer in a keyboard/power management controller, a system BIOS is also provided, by which the entire system thereof is controlled.
As mentioned above, in a conventional notebook PC, a microcomputer provided with keyboard/power management BIOS and a flash memory containing a system BIOS are provided and they are built in as separate chips. Also, in a microcomputer provided with a keyboard/power management BIOS, in order to reduce the area of address space/interrupt vector space, register address/interrupt vector is shared by plural modules. Further, in order to reduce the number of terminals, a single terminal is provided with several functions.
Meanwhile, examinations of the technique for such a microcomputer of a notebook PC as mentioned above by the inventors of this invention have revealed the followings.
For example, since the keyboard/power management BIOS and the system BIOS are built in each of the separate chips in the conventional notebook PC mentioned above, the area of a board is inevitably increased. Further, since the system BIOS is built in the chip of a flash memory, it has a problem of security.
Furthermore, in order to reduce the area of address space/interrupt vector space, register address/interrupt vector is shared by plural modules in the microcomputer provided with the keyboard/power management BIOS. Therefore, when creating a program, it is necessary always to be aware of which module is controlled. As a result, its usability is not so high. Moreover, since a single terminal is provided with several functions in order to reduce the number of terminals, there are many pin multiplexes, and there is a problem that some of functions cannot be used simultaneously.